Those Ducati Winglets: What Are They Really For?
The Ducati Desmosedici MotoGP bike has always been famous for its top speed, a characteristic which is generally put down to two things: the first is the 16-valve V4 desmodromic engine, the brainchild of Ducati Corse director Filippo Preziosi, which has long been the most powerful engine on the grid. The second factor is the Bologna company's focus on aerodynamics, an area that other factories have spent much less time and attention on. The extremely slippery nature of the Ducati Desmosedici is in large part due to Ducati Corse's use of former F1 engineer Alan Jenkins as an aerodynamics consultant.
Jenkins has worked ceaselessly with Ducati over the years to improve the aerodynamics of the Desmosedici, and the German Grand Prix at the Sachsenring saw a new innovation appear on the fairing of the bike. The Ducati had sprouted a pair of "winglets" (shown below) - protruberances sticking both forward and out of the side of the fairing, at about the height of bottom of the fork outer. Naturally, these strange additions aroused the curisoity of the assembled media, who set about trying to fathom their purpose.
Questions aimed at Ducati riders Casey Stoner and Nicky Hayden did not produce any usable information, both men merely replying that they could not really feel much difference. The general consensus - prodded by some inside information - was that the point of the winglets was to increase downforce at high speed, and prevent the bike's propensity to lift the front wheel. That story was mulled over by the assembled wise heads in the paddock, and generally assumed to be probably accurate.
But just how correct that supposition is remains to be seen. For after an astute post by one member of MotoMatters.com, there are reasons to believe that the downforce idea is little more than smoke and mirrors. For a start, the surface area involved is relatively small, most likely too small to have much of an effect at the required velocities. Figures being bandied about the paddock suggested that the winglets contributed around 10 kg of downforce at 300 km/h, which would be enough to prevent the front wheel from lifting.
That figure may be correct, but preventing the front from lifting is far more of a problem at 200 km/h than it is at 300 km/h. At that point, the bike is under hard acceleration, and is wanting to lift the front. Anti-wheelie software can help here, but that relies on cutting power, something that reduces drive out of the corners. Some form of aerodynamic assistance would be of more use than cutting power, but due to the exponential nature of fluid dynamics (air resistance - and the effectiveness of flaps and winglets - is squared when speed doubles), the effectiveness of the winglets is likely to be around half that 10 kg figure at 200 km/h. And the slower you go (and therefore, the harder you are accelerating), the less effective the winglets become.
But while the focus has been almost entirely on the horizontal surfaces, the real magic is probably being created by the vertical flaps. The inverted shark fin shapes sticking out below the protrusions appear to be shaping airflow along the side of the fairing, and reducing the air pressure behind the winglets. The horizontal protrusions could be part of a scheme to increase the airflow past the vertical fins, which as a result of the Venturi effect reduces the pressure behind the fins.
And what do we find directly behind those winglets? The radiator vents, where hot air from the radiator is being forced out of the fairing, dispersing the heat from the Desmosedici engine, a notorious problem for the Ducati. The problem with the bare radiator vents is that the air exiting the vents hits the wall of air at the side of the fairing, reducing the flow from the vents. The vents are shaped to smooth and maximize the airflow around the vents, but the usual fairing design soon runs into limits with how much the venting of hot radiator air can be optimized.
The winglets - and especially the vertical flaps - produce an extra pressure drop over the radiator vents by accelerating the flow over them. That decrease in pressure sucks more hot air out of the radiator vents, which in turn draws more cool air through the radiator, allowing the engine to run cooler. The location of the winglets is directly ahead of the largest part of the radiator vents, and the place which would produce the most benefit from increased airflow. The shape of the vertical flaps also suggests they could play a role in smoothing airflow over the vents, and separating the boundary layer from the vent.
The idea that the winglets seen on the Ducati are more to do with cooling than with downforce has a lot of things going for it. First and foremost, it fits in with the biggest change in MotoGP this season, the restrictions on the numbers of engines which may be used. With just 6 engines per season for each rider, engine longevity becomes crucial, and one of the key elements in securing that longevity is engine temperature. The lower the temperature the engine operates at, the longer it will last. Ducati MotoGP bikes have always run extremely hot - the factory was forced to drill holes in the fairing on the first version of the bike back in 2003, to prevent the heat from the engine from causing heat blisters on the hands of Loris Capirossi and Troy Bayliss - and though the issue has been worked on throughout the bike's history, the Ducati still generates an awful lot of heat.
So an aerodynamic solution to reducing the operating temperature is not only plausible, but extremely likely, given Ducati's interest in the area. The size, shape and location of the winglets suggest that this is exactly what Ducati have been trying to achieve, to cool the engine by producing better airflow through the radiators, with the winglets in effect sucking the hot air out of the back of the vents more efficiently.
Whether this was the intent of Alan Jenkins and Filippo Preziosi when they put this solution together or not will probably remain a secret, at least for the time being. The talk of increasing downforce helps create confusion and may be helping to cover Ducati's tracks. The fact that the MotoGP paddock - as full of brilliant minds as it is - has neither the experience nor the interest (one Moto2 bike designer dismissed the idea of aerodynamics as a factor in motorcycle racing as completely irrelevant) in understanding the implications of aerodynamics innovations merely plays into Ducati's hands even further.
I can claim no credit for the ideas in the above article: They were taken from the comments by MotoMatters.com member Oscar both on the main site as well as on the forum, and mixed up with other comments from forum members until the above synopsis emerged. Any credit belongs to them, and any errors are entirely mine.